DE19533607A1 - Positive working radiation sensitive mixture and process for the production of relief structures - Google Patents

Description

The invention relates to positive working radiation-sensitive Mixtures, the acid labile groups and photoactive compo contain elements that are sensitive to actinic radiation and have improved contrast. This radiation sensitive Liche mixtures are particularly suitable as resist materials for Deposit resists for the production of relief patterns.

Positive-working radiation-sensitive mixtures based on the The principle of "chemical amplification" is based knows. In this way, in a primary photoreaction he becomes a species testifies which is then a catalytic irrespective of the radiation Triggers secondary reaction and thereby the sensitivity dra table increased. Such systems that are photochemically strong He generate acid, which is then acid labile in a secondary reaction Splitting groups are e.g. From U.S. Patent 3,923,514; U.S. Patent 3,915,706 and DE-A 34 06 927 known.

The contrast of such resists, i.e. H. the "sharpness" at the Differentiation between unexposed and exposed areas is an important application parameter. Therefore Ver always wanted to improve contrast.

The object of the present invention is a radiation show sensitive mixture, the very good light sensitivity lightness, good processing latitude, no layer thickness ver lust between the different process steps and relief structures with improved contrast.

This task can be surprisingly by the Invention according to positive working radiation-sensitive mixtures to solve.

The present invention relates to
Positive working radiation sensitive mixtures consisting essentially of

• (a) at least one poly containing acid-labile groups that is insoluble in water due to the action of acid in aqueous-alkaline solutions become soluble,  
• (b) at least one organic compound which, under the action of effect of actinic radiation produces an acid, and
• (c) at least one other organic (b) different Connection,

which are characterized in that the polymer (a) units of the formulas (I), (II) and (III)

built-in, with the proviso that
37-60 mol% units of the formula (I)
38-48 mol% units of formula (II) and
0-15 mol% of units of the formula (III)
are contained as structural units of the polymer,
the organic compounds (b) a sulfonium salt of the formula (IV)

and the organic compound (c) of the formula (V)

corresponds in which R ′ with R ′ ′ are the same or different from one another are and represent alkyl radicals having 1 to 4 carbon atoms or R 'with R' 'together to form a five-membered group via CH₂ groups Ring are linked, and R '' 'for an alkyl radical having 1 to 4 Carbon atoms.

It is preferred if in formula (V) the organic compound (c) R ', R' 'and R' '' represent CH₃.

The mixtures according to the invention are preferably in the form of a solution in an organic solvent or solvent mixture. It is also preferred that components (a), (b), and (c) in amounts
from 90 to 97.99 percent by weight (a),
from 2 to 8 percent by weight (b) and
from 0.01 to 2 percent by weight (c)
be used.

The present invention also relates to a method for Manufacture of photosensitive coating materials, wherein radiation-sensitive mixtures according to the invention are used will.

The present invention also relates in particular to a Process for the production of relief structures by application a radiation-sensitive mixture in a layer thickness of 0.1 to 5 µm on a substrate pretreated in the usual way, Drying at temperatures from 70 to 150 ° C, imagewise exposure, optionally heating to temperatures of 40 to 160 ° C, and Develop with an aqueous alkaline solution, using radiation sensitive mixtures used according to the present invention will.

Draw the radiation-sensitive mixtures according to the invention are characterized by low absorption of UV radiation and result therefore steep flanks in the relief and they have very good light temp  sensitivity (approx. 30 mJ / cm²), so that it is very good for ver work in deep UV steppers. More very essential Liche advantages are that contrast and "depth of focus" improves are, so that structures of 0.25 µm even with layer thickness swan can be produced reproducibly.

The very good processing latitude is particularly advantageous the exposed wafer, so that even after an hour can be structured reproducibly after their exposure, and that no loss of layer thickness between the different Process steps, such as baking out and developing, occur.

To the structural components of the radiation sensitivity according to the invention The following mixtures are to be carried out in detail.

The polymers (a) to be used according to the invention generally have molecular weights (M _w ) between 2000 and 100000, preferably between 4000 and 30000 and can be obtained, for example, from poly (p-hydroxystyrene) or preferably additionally non-aromatic cyclic alcohol units (vinylcyclohexanol) 4-A units) in amounts up to 15 mol% containing poly (p-hydroxystyrene), for. B. by polymer-analogous reaction with appropriate men gene tetrahydropyran in the presence of acid. A corresponding method can be found in EP-342 498-B (DE-A-38 17 012).

As starting products for the production of an according to the invention setting polymers (a) are also suitable, for example, partially hydrogenated poly- (p-hydroxystyrenes), such as the J 01 103 604-A and EP-A-0 401 499 can be found.

The polymer (a) contains the units of the formulas (I), (II) and (III) in amounts of
37-60 mol% of units of the formula (I),
38-48 mol% units of formula (II) and
0-15 mol% of units of formula (III) incorporated.

If the polymer (a) has no units of the formula (III) builds, are preferably 60 ± 10 mol% units of the formula (I) and 40 ± 10 mol% units of formula (II) as a structure units installed.

However, polymer (a) particularly preferably contains units of Formula (III) in amounts of up to 15, preferably 10 ± 4 mol% based on the total amount of structural units of the formulas (I), (II) and (III) incorporated in mol% as structural units.  

Component (a) is radiation-sensitive in the invention Mixture generally in amounts of 90 to 97.99, preferably 93 to 95.99 weight percent, based on the total amount of Components (a) + (b) + (c) included.

As an organic compound (b) which, under the action of acti generated an acidic radiation, according to the invention Sulfonium salt of the forms (IV) used. The production of Sulfonium salts are state of the art. For example, it can after a in J. Polym. Sci., Chem. Ed., 18, 1021 (1980) be written synthesis instructions take place. The organic ver Bond (b) is radiation-sensitive in the invention Mixture generally in an amount of 2 to 8, preferably 3 up to 6 percent by weight, based on the total amount of components ten (a) + (b) + (c) included.

The organic to be used according to the invention as component (c) Compound corresponds to the formula (V), wherein R ′, R ′ ′ and R ′ ′ ′ below are identical or different from one another and for alkyl radicals with 1 up to 4 carbon atoms, e.g. B. methyl, ethyl, propyl, iso propyl, n-butyl or isobutyl radicals or R 'with R' 'with linked to each other via CH₂ groups to form a five-membered ring are. Preferably R ', R' 'and R' '' represent CH₃.

The preparation of such compounds (c) can, for example by reacting a 2-methyl-4-hydroxy-5-isopropyl-phenyl-dial kylsulfonium triflate with approximately equimolar amounts of tetramethyl ammonium hydroxide take place, for example in the presence of inert tem solvent, such as. B. in alkanols.

Component (c) is radiation-sensitive in the invention Mixture generally in amounts of 0.01 to 2, preferably 0.05 to 1 percent by weight based on the total amount of the com component (a) + (b) + (c) included.

The radiation-sensitive mixture according to the invention can additionally Lich other, conventional, corresponding to the prior art Auxiliaries and additives (sensitizers, dyes, flow tools, network aids, stabilizers, etc.) included. These additives generally become smaller in quantities 3 wt .-% added.

The mixtures according to the invention are used to produce resists preferably in a suitable inert polar organic solvent Solvent dissolved, the solids content usually in Range is between 5 and 40 wt .-%. Come as a solvent in principle aliphatic ketones, alcohols, ethers and esters, and  Mixtures of the same in question. Alkylene is particularly preferred glycol monoalkyl ethers such as ethyl cellosolve, butyl glycol, methyl cellosolve and 1-methoxy-2-propanol, Alkylene glycol alkyl ether esters, such as Methyl cellosolve acetate, methyl propylene glycol acetate and ethyl propylene glycol acetate, ketones, such as cyclohexanone, Cyclopentanone and methyl ethyl ketone, and acetates such as butyl acetate, ethyl acetate, other esters such as ethyl lactate and butyro lactone and their mixtures with aromatics such as toluene and xylene. The selection of the corresponding solvents, as well as their Mi conditions depends on the solubility of the mixture components (a) + (b) + (c).

Other additives such as adhesion promoters and softeners can also be used Macher be added, generally in amounts of up to 1% by weight.

The radiation-sensitive mixtures according to the invention are sen sititive to X-ray, electron and UV radiation. Give Otherwise, sensitizers can be added in small amounts such as pyrene and perylene to the compounds in the longer-wave UV up to the visible wavelength range to raise awareness. For exposure in special wavelengths ranges, such as in short-wave UV (<300 nm), is a high transparency of the layers in the respective Exposure wavelength required. In common exposure devices based on mercury lamps, the 254 nm line or excimer lasers are used which emit at 248 nm (KrF). Radiation sensitive recording materials should therefore have the lowest possible optical densities in this area.

In the process according to the invention for producing sensitive coating materials and for the production of posi tive relief patterns becomes a radiation sensitive record tion layer, which essentially consists of the invention radiation-sensitive mixture exists, figuratively in such a do sis irradiated that the solubility of the exposed areas after a thermal baking step at temperatures between 40 and 160 ° C in aqueous alkaline solvents increases and this Areas are selectively removed with the alkaline developer can.

Contain the radiation-sensitive mixture according to the invention tend photoresist solutions are generally in layer thicknesses from 0.1 to 5 µm, preferably 0.5 to 1.5 µm to suitable ones Substrates, for example surface oxidized silicon wafers applied by spin coating, dried  (e.g. at temperatures between 70 and 150 ° C) and with a suitable light source imagewise exposed through a photomask, e.g. B. with short-wave UV rays (deep UV) with wavelengths between 200 and 300 nm. Particularly suitable light sources are Excimer laser from KrF (248 nm). After imagewise exposure is - if necessary after a short bake (postbake) at Tem temperatures up to 160 ° C - with usual aqueous alkaline developments solutions - generally at pH values between 12 and 14 - developed, whereby the exposed areas are washed out. The resolution is in the submicron range. The for the fiction exposures required according to radiation-sensitive mixtures Energy is generally between 10 and 300 mJ / cm² Layer thicknesses of 1 µm.

Draw the radiation-sensitive mixtures according to the invention improved through high sensitivity, good resolution Contrast, improved depth of focus and increased processing leeway and are therefore particularly advantageous for shortwave lithography.

The parts mentioned in the examples and comparative examples and percentages are steep unless otherwise specified or percentages by weight.

The "depth of focus" was determined analogously to that of Chris A. Mack in Microlithography World, Spring 1995, pages 20 through 21, U.S.A.

The contrast of the resist, expressed by means of the gamma value (Γp), was obtained by plotting the layer thickness against Belich dose determined. The gamma value is for positive resist systems defined as

where D₀ and D₁ the extrapolized exposure energy doses the dark erosion energy curve.

Comparative Example 1

A photoresist solution was made up of 5 parts 2-methyl-4-hydroxy-5-isopropylphenyldimethylsulfonium triflate and 95 parts of poly- [4-hydroxystyrene-co-4-tetrahydropyranyloxy styrene-co-vinylcyclohexanol-4] (molar ratio of the comono meren = 39: 45: 6) and 400 parts of ethyl lactate. After  This solution was dissolved by a filter filtered with a pore diameter of 0.2 microns.

An approx. 0.8 µm thick layer of this solution was applied to the top surface oxidized silicon wafer spun on and at 1 min Baked 130 ° C. After exposure through a structured Test mask with Ecimer laser light with a wavelength of 248 nm was the Baked wafer at 130 ° C for 1 min and then with an aqueous alkaline developer developed 1 min.

After measuring the remaining photoresist layers, the Contrast of the resist determined. The gamma value was 6.

example 1

A photoresist solution was made up of 5 parts 2-methyl-4-hydroxy-5-isopropylphenyldimethylsulfonium triflate, 0.1 parts of the organic compound (c) of the forms (V), wherein R ′, R ′ ′ and R ′ ′ ′ are methyl groups, and 95 parts of poly- [4-hydroxy styrene-co-4-tetrahydropyranyloxystyrene-co-vinylcyclohexanol-4] (molar ratio of the comonomers = 39: 45: 6) and 400 parts Produced ethyl lactate. After the input materials were dissolved this solution through a filter with a pore diameter of 0.2 µm filtered and processed analogously to Comparative Example 1. Of the found gamma value of this solution is 8.

Comparative Example 2

A photoresist solution was made up of 5 parts 2-methyl-4-hydroxy-5-isopropylphenyldimethylsulfonium triflate and 95 parts of poly- [4-hydroxystyrene-co-4-tetrahydropyranyloxy styrene-co-vinylcyclohexanol-4] (molar ratio of the comono meren = 52: 40: 8) and 400 parts of ethyl lactate. After This solution was dissolved by a filter filtered with a pore diameter of 0.2 microns.

After processing according to Example 1, a gamma value of 6.5 determined experimentally.

Example 2

A photoresist solution was made up of 5 parts 2-methyl-4-hydroxy-5-isopropylphenyldimethylsulfonium triflate, 0.1 part of the organic compound (c) of formula (V), wherein R ′, R ′ ′ and R ′ ′ ′ are methyl groups, and 95 parts of poly- [4-hydroxy styrene-co-4-tetrahydropyranyloxystyrene-co-vinylcyclohexanol-4]  (molar ratio of the comonomers = 52: 40: 8) and 400 parts Produced ethyl lactate. After processing according to example 1 a gamma value of 9 was determined experimentally.

Comparative Example 3

A photoresist solution was made up of 6 parts 2-methyl-4-hydroxy-5-isopropylphenyldimethylsulfonium triflate and 94 parts of poly- [4-hydroxystyrene-co-4-tetrahydropyranyloxy styrene-co-vinylcyclohexanol-4] (molar ratio of the comono meren = 47: 40: 13) and 400 parts of ethyl lactate. After This solution was dissolved by a filter filtered with a pore diameter of 0.2 microns.

After processing according to Example 1, a gamma value of 6.5 determined experimentally.

Example 3

A photoresist solution was made up of 6 parts 2-methyl-4-hydroxy-5-isopropylphenyldimethylsulfonium triflate, 0.1 part of the organic compound (c) of formula (V), wherein R ′, R ′ ′ and R ′ ′ ′ are methyl groups, and 94 parts of poly- [4-hydroxy styrene-co-4-tetrahydropyranyloxystyrene-co-vinylcyclohexanol-4] (molar ratio of the comonomers = 47: 40: 13) and 400 parts Produced ethyl lactate. After processing according to example 1 a gamma value of 10 was determined experimentally.

Comparative Example 4

A photoresist solution was made up of 5 parts 2-methyl-4-hydroxy-5-isopropylphenyldimethylsulfonium triflate and 95 parts of poly- [4-hydroxystyrene-co-4-tetrahydropyranyloxy styrene-co-vinylcyclohexanol-4] (molar ratio of the comono meren = 42: 45: 13) and 345 parts of ethyl lactate. After This solution was dissolved by a filter filtered with a pore diameter of 0.2 microns.

An approx. 1 µm thick resist layer was applied to the top of this solution surface oxidized silicon wafers spun on.

After further processing according to Example 1, a gamma value was obtained of 7.5 determined experimentally.  

Example 4

A photoresist solution was made up of 5 parts 2-methyl-4-hydroxy-5-isopropylphenyldimethylsulfonium triflate, 0.15 parts of the organic compound (c) of formula (V), wherein R ′, R ′ ′ and R ′ ′ ′ are methyl groups, and 95 parts of poly- [4-hydroxy styrene-co-4-tetrahydropyranyloxystyrene-co-vinylcyclohexanol-4] (molar ratio of the comonomers = 42: 45: 13) and 400 parts Produced ethyl lactate. After processing according to example 1 a gamma value of 12 was determined experimentally.

Comparative Example 5

A photoresist solution was made up of 4 parts 2-methyl-4-hydroxy-5-isopropylphenyldimethylsulfonium triflate and 96 parts of poly- [4-hydroxystyrene-co-4-tetrahydropyranyloxy styrene-co-vinylcyclohexanol-4] (molar ratio of the comono meren = 49: 38: 13) and 400 parts of ethyl lactate. After This solution was dissolved by a filter filtered with a pore diameter of 0.2 microns.

After further processing according to Example 1, a gamma value was obtained of 6.4 determined experimentally.

Example 5

A photoresist solution was made up of 4 parts 2-methyl-4-hydroxy-5-isopropylphenyldimethylsulfonium triflate, 0.15 parts of the organic compound (c) of formula (V), wherein R ′, R ′ ′ and R ′ ′ ′ are methyl groups, and 96 parts of poly- [4-hydroxy styrene-co-4-tetrahydropyranyloxystyrene-co-vinylcyclohexanol-4] (molar ratio of the comonomers = 49: 38: 13) and 400 parts Produced ethyl lactate. After processing according to example 4 a gamma value of 9 was determined experimentally.

The additives in the examples claimed in the invention len 1, 2, 3, 4, 5 show better properties of the examined Photoresists.

These improved properties can still be used in the measurement the depth of focus can be determined.

The additive claimed according to the invention improves the depth of Focus, which leads to a greater processing latitude.  

Example 6

A photoresist solution, prepared according to Example 1, was on one with an approx. 100 nm thick anti-reflective coating (e.g. ARC®CD9 from Brewer Science, Inc. Rolla, MO, U.S.A.) silicon wafers (diameter 200 mm) in a layer thickness of 700 nm and baked at 130 ° C.

After exposure with a wafer stepper from ASM Litho The wafer was made graphy with different depths of focus heated and in a spray developer with an aqueous alkaline Medium developed.

The line widths were used to determine the depth of focus different focus measured. The following results were receive:

A comparative sample according to Comparative Example 1 without the However, addition of component (c) according to the invention showed worse results:

Comparative Example 7

Another 3 part resist formulation 2-methyl-4-hydroxy-5-isopropylphenyldimethylsulfonium triflate and 97 parts of poly- [4-hydroxystyrene-co-4-tetrahydropyranyloxy styrene-co-vinylcyclohexanol-4] (molar ratio of the comono meren = 46: 45: 9) and 400 parts of ethyl lactate was correspondingly Example 6 processed. The lines were measured at 250 nm broad structures

Example 7

The resist formulation of Comparative Example 7 was 0.1 part the organic compound (c) of the formula (V), in which R ′, R ′ ′ and R '' 'are methyl groups, mixed. This can be compared Comparative Example 7 achieve significantly better results:

Comparative Example 8

A photoresist solution was made up of 5 parts 2-methyl-4-hydroxy-5-isopropylphenyldimethylsulfonium triflate and 95 parts of poly- [4-hydroxystyrene-co-4-tetrahydropyranyloxy styrene] (molar ratio of the comonomers = 60:40) and 400 parts len ethyl lactate produced. After dissolving the input materials this solution was passed through a filter with a pore diameter filtered from 0.2 µm.

An approx. 0.8 µm thick layer of this solution was applied to the top surface oxidized silicon wafer spun on and at 1 min Baked 130 ° C. After exposure through a structured Test mask with excimer laser light of wavelength 248 nm was the Baked wafer at 130 ° C for 1 min and then with an aqueous alkaline developer developed 1 min.

After measuring the remaining photoresist layers, the Contrast of the resist determined. The Garnina value was 6.4.

Example 8

A photoresist solution was made up of 5 parts 2-methyl-4-hydroxy-5-isopropylphenyldimethylsulfonium triflate, 0.1 part of the organic compound (c) of formula (V), wherein R ′, R ′ ′ and R ′ ′ ′ are methyl groups and 95 parts of poly- [4-hydroxy styrene-co-4-tetrahydropyranyloxystyrene] (molar ratio of Comonomers = 60:40) and 400 parts of ethyl lactate. After This solution was dissolved by a filter filtered with a pore diameter of 0.2 µm and analogous to Bei game 1 processed. The gamma value is 7.5.  

Comparative Example 9

A photoresist solution was made up of 4 parts 2-methyl-4-hydroxy-5-isopropylphenyldimethylsulfonium triflate and 96 parts of poly- [4-hydroxystyrene-co-4-tetrahydropyranyloxy styrene] (molar ratio of the comonomers = 59: 41) and 400 parts len ethyl lactate produced. After dissolving the feed this solution was passed through a filter with a pore diameter filtered from 0.2 µm.

After processing according to Example 1, a gamma value of 6.5 determined experimentally.

Example 9

A photoresist solution was made up of 4 parts 2-methyl-4-hydroxy-5-isopropylphenyldimethylsulfonium triflate, 0.1 part of the organic compound (c) of formula (V), wherein R ′, R ′ ′ and R ′ ′ ′ are methyl groups, and 96 parts of poly- [4-hydroxy styrene-co-4-tetrahydropyranyloxystyrene] (molar ratio of Comonomers = 59: 41) and 400 parts of ethyl lactate. After the processing according to Example 1 was a gamma value of 8.4 determined experimentally.

Claims (7)

1. Positive working radiation-sensitive mixture consisting essentially of

• (a) at least one polymer containing acid-labile groups which is insoluble in water and becomes soluble in aqueous alkaline solutions by the action of acid,
• (b) at least one organic compound which generates an acid under the action of actinic radiation, and
• (c) at least one further organic compound different from (b),

characterized in that the polymer (a) units of the formulas (I), (II) and (III) built-in, with the proviso that
37-60 mol% units of the formula (I)
38-48 mol% units of formula (II) and
0-15 mol% of units of the formula (III)
are contained as structural units of the polymer,
the organic compound (b) a sulfonium salt of the formula (IV) and the organic compound (c) of the formula (V) corresponds in which R ′ with R ′ ′ are identical or different from one another and stand for alkyl radicals having 1 to 4 carbon atoms or R ′ with R ′ ′ are linked to one another via CH₂ groups to form a five-membered ring and R ′ ′ ′ for an alkyl radical with 1 to 4 carbon atoms. 2. Mixture according to claim 1, characterized in that in For mel (V) of the organic compound (c) R ′, R ′ ′ and R ′ ′ ′ for CH₃ stand. 3. Mixture according to claim 1 or 2, characterized in that it in the form of a solution in an organic solvent or solvent mixture is present. 4. Mixture according to claim 1 or 2, characterized in that the components (a), (b), and (c) in quantities
from 90 to 97.99 percent by weight (a),
from 2 to 8 percent by weight (b) and
from 0.01 to 2 percent by weight (c)
be used. 5. Process for making photosensitive coating materials, characterized in that a radiation sensitive mixture according to one of claims 1 to 4 is set. 6. Process for the production of relief structures by Auf carry a radiation sensitive mixture in one Layer thickness of 0.1 to 5 microns in a conventional manner treated substrate, drying at temperatures of 70 to 150 ° C, imagewise exposure, heating if necessary to temperatures of 40 to 160 ° C, and developing with a aqueous alkaline solution, characterized in that a radiation-sensitive mixture according to one of the claims 1 to 4 is used.